Can you prepurchas tickets at Costco for Space Needle?

Unsure, but we used the kiosk which was pretty quick.

Kiosk was fasstt

We got the blast pass at the ticket counter and went right up

Yes, self service kiosk works great. There's no lines and waiting.

I just get them at the kiosk.

Yes

Groupon has good deals

We bought them at the entrance.

Not a member.

I did not and am unsure. I got mine thru Groupon.